Royal Institution of Great Britain. 18T 



forms a small part of the whole expense, the specific heats may be 

 safely neglected, leaving the numbers, 162, 96, and 37, to represent 

 the expense of elevating to the boiling temperature equal volumes 

 of water, alcohol, and ether. 



The cost of vaporizing them will be given by multiplying the 

 actual weights (represented by their specific gravities) of the three 

 liquids by their latent heats, which are about 1000, 450, and 300. 



Weight. Latent Heat. 



Water . 1000 x 1000 = 1000 

 Alcohol . 800 X 450 = 360 

 Ether . 740 x 800 = 222 



Add these numbers to those representing the cost of heating up 

 to the boiling points, respectively : 



162 + 1000 = 1162 Water 

 96 + 360 = 456 Alcohol 

 37 + 222 = 259 Ether 



then the last results will express the whole cost of vaporizing equal 

 bulks of the liquids in question ; the advantage, so far, appearing 

 greatly in favour of the ether and alcohol, as compared with water. 

 But it is now necessary to introduce another element into the cal- 

 culation, namely, the specific gravity of the vapour, or the volumes 

 of vapour produced from equal volumes of liquid. These are 

 nearly as the following numbers : 



Water . . . 1700 



Alcohol . . 610 



Ether ... 800 



That is to say, one cubic inch of water becomes about 1700 inches of 

 steam, at atmospheric pressure ; and single cubical inches of alcohol 

 and ether become 610 and 300 inches, at the same pressure. The 

 quantity of power is obviously as the bulk of the vapour, and the 

 cost is of consequence inversely as that bulk. If, therefore, the 

 cost of vaporizing be divided by the bulks of vapour respectively, 

 the quotients will represent the relative expense of equal units of 

 power derived from the three liquids. 



1162 -r 1700 == .6714 Water. 

 456 -f- 610 = .7475 Alcohol. 

 259 -h 300 = .8633 Ether. 



From which it appears, that, independently of the original cost of 

 the liquid, supposing, indeed, that alcohol and ether were supplied 



